<s>
HP	O
Reliable	O
Transaction	O
Router	B-Protocol
(	O
RTR	O
)	O
is	O
a	O
transactional	O
middleware	B-General_Concept
for	O
computer	O
software	O
,	O
marketed	O
by	O
Hewlett	O
Packard	O
.	O
</s>
<s>
RTR	O
manages	O
the	O
messages	O
which	O
are	O
sent	O
between	O
client-server	O
to	O
provide	O
node	B-Protocol
and	O
network	O
fail-over	O
for	O
increased	O
reliability	B-Protocol
,	O
transactional	O
integrity	O
,	O
and	O
interoperability	O
between	O
dissimilar	O
systems	O
.	O
</s>
<s>
The	O
RTR	O
software	O
has	O
three	O
logical	O
entities	O
and	O
referred	O
to	O
as	O
front-end	O
(	O
FE	O
)	O
,	O
back-end	O
(	O
BE	O
)	O
and	O
transaction-router(TR )	O
.	O
</s>
<s>
The	O
router	B-Protocol
is	O
a	O
software	O
component	O
that	O
provides	O
the	O
fail-over	O
intelligence	O
and	O
manages	O
connections	O
to	O
the	O
back-end	O
.	O
</s>
<s>
The	O
client	O
applications	O
running	O
on	O
the	O
Front-End	O
combined	O
with	O
Router	B-Protocol
and	O
Server	B-Application
applications	I-Application
running	O
on	O
back-end	O
interact	O
to	O
provide	O
transaction	O
integrity	O
and	O
reliability	B-Protocol
.	O
</s>
<s>
The	O
three	O
logical	O
entities	O
can	O
exist	O
on	O
the	O
same	O
node	B-Protocol
but	O
are	O
usually	O
deployed	O
on	O
different	O
nodes	O
to	O
achieve	O
modularity	O
,	O
scalability	O
and	O
high	O
availability	O
.	O
</s>
<s>
The	O
client	O
application	O
interacts	O
with	O
the	O
front-end	O
which	O
forwards	O
the	O
messages	O
to	O
the	O
router	B-Protocol
,	O
the	O
router	B-Protocol
in	O
turn	O
routes	O
the	O
message	O
to	O
the	O
intended	O
back-end	O
where	O
the	O
appropriate	O
Server	B-Application
application	I-Application
is	O
available	O
for	O
processing	O
the	O
message	O
.	O
</s>
<s>
The	O
message	O
exchange	O
happens	O
between	O
the	O
client	O
and	O
server	B-Application
.	O
</s>
<s>
RTR	O
can	O
help	O
survive	O
the	O
failures	O
generally	O
seen	O
in	O
distributed	O
application	O
environment	O
which	O
include	O
complete	O
site	O
failure	O
,	O
node	B-Protocol
failure	O
,	O
network	O
link	O
failure	O
and	O
software	O
process	O
failure	O
.	O
</s>
<s>
When	O
RTR	O
and	O
its	O
components	O
are	O
running	O
along	O
with	O
the	O
applications	O
,	O
then	O
Client	O
Application	O
,	O
Server	B-Application
Application	I-Application
,	O
RTR	O
services	O
will	O
be	O
active	O
.	O
</s>
<s>
The	O
C	O
,	O
C++	B-Language
,	O
Java	B-Language
and	O
.Net	B-Application
variants	O
of	O
APIs	O
are	O
available	O
for	O
creating	O
applications	O
to	O
use	O
RTR	O
.	O
</s>
<s>
The	O
initial	O
release	O
was	O
written	O
in	O
a	O
mix	O
of	O
Macro	O
,	O
Bliss	O
,	O
Pascal	O
and	O
SDL	O
on	O
top	O
of	O
DECnet	O
and	O
VMS	B-Operating_System
.	O
</s>
<s>
Later	O
it	O
was	O
reimplemented	O
in	O
C	O
on	O
top	O
of	O
a	O
TCP/IP	O
stack	O
and	O
an	O
OS	O
agnostic	O
infrastructure	O
,	O
that	O
allowed	O
it	O
to	O
be	O
deployed	O
on	O
multiple	O
operating	O
systems	O
,	O
including	O
various	O
flavors	O
of	O
Unix/Linux	O
,	O
VMS	B-Operating_System
,	O
Windows	B-Application
.	O
</s>
<s>
A	O
Java	B-Language
and	O
C++	B-Language
veneer	O
was	O
added	O
in	O
the	O
mid	O
90s	O
to	O
support	O
a	O
RPC	O
style	O
veneer	O
,	O
on	O
top	O
of	O
the	O
"	O
services	O
"	O
oriented	O
interface	O
.	O
</s>
<s>
RTR	O
was	O
one	O
of	O
the	O
first	O
OLTP	O
middleware	B-General_Concept
services	O
that	O
provided	O
the	O
following	O
features	O
(	O
in	O
addition	O
of	O
the	O
usual	O
ones	O
)	O
,	O
viz	O
.	O
</s>
<s>
RTR	O
was	O
available	O
on	O
HP-UX	B-Application
,	O
Linux	B-Application
,	O
Windows	B-Application
and	O
OpenVMS	B-Operating_System
in	O
2010	O
.	O
</s>
